Week 4 Materials

The question

Suppose you were considering investing in one of these two companies. Which one would you choose? Why?

Gravia

A Virginia Tech student has created a floor lamp powered by gravity.

Clay Moulton of Springfield, Va., who received his Master of Science in Architecture with a concentration in industrial design from the College of Architecture and Urban Studies in 2007, created the lamp as a part of this master’s thesis. The LED lamp, named Gravia, has just won second place in the Greener Gadgets Design Competition as part of the Greener Gadgets Conference in New York City.

Concept illustrations of Gravia depict an acrylic column a little over four feet high. The entire column glows when activated. The electricity is generated by the slow fall of a mass that spins a rotor. The resulting energy powers 10 high-output LEDs that fire into the acrylic lens, creating a diffuse light. The operation is silent and the housing is elegant and cord free – completely independent of electrical infrastructure.

The light output will be 600-800 lumens – roughly equal to a 40 watt incandescent bulb. Each drop of the gravity mechanism runs the light over a period of four hours.

To "turn on" the lamp, the user moves weights from the bottom to the top of the lamp. An hour-glass like mechanism is turned over and the weights are placed in the mass sled near the top of the lamp. The sled begins its gently glide back down and, within a few seconds, the LEDs come on and light the lamp, Moulton said. “It’s more complicated than flipping a switch but can be an acceptable, even enjoyable routine, like winding a beautiful clock or making good coffee,” he said.

Moulton estimates that Gravia’s mechanisms will last more than 200 years, if used eight hours a day, 365 days a year. “The LEDs, which are generally considered long-life devices, become short-life components in comparison to the drive mechanisms,” he said.

The acrylic lens will be altered by time in an attractive fashion, Moulton said. “The LEDs produce a slightly unnatural blue-ish light. As the acrylic ages, it becomes slightly yellowed and crazed through exposure to ultraviolet light,” he said. “The yellowing and crazing will tend to mitigate the unnatural blue hue of the LED light. Thus, Gravia will produce a more natural color of light with age.”

He predicted that the acrylic will begin to yellow within 10 to 15 years when Gravia is used in a home’s interior room.

Deciwatt

Deciwatt offers a similar product to the one described by Gravia. This is from their frequently asked questions page:

How does it work?

"After the bag has been lift-up by human force, The gravity exerts a force on a weight and while the weight is descending under that force, this kinetic energy is converted via a series of small gears into electrical energy and the light is powered live. There are no batteries in GravityLight. The duration of the drop is 28min on low light, 20min on medium and 12min on high. It can be used over and over with no running costs."

What is the power of GravityLight?

To this question there are two answers: the power output of the GravityLight in Watts, and the Lumens/Watt of the LED. The power output is (with a 12.5kg load) H: 0.1W, M: 0.075W and L: 0.05W. The lumens/watt of the LED is in the region of 100 l/w. So on High you will have about 15 lumens output, Med about 10 lumens, and Low about 5 lumens. The advantage of an LED light source over a kerosene lamp is that nearly all this light output can be directed at a task or onto a surface.

Questions:

1. Explain how each device is supposed to work
2. Where does the energy come from in each device?
3. How much energy does each device have available?
4. How much energy does each claim to use?
5. Are both products workable?
6. Are both products equally useful,assuming they work as claimed?
7. Which one is a better choice? Why?